Frequently asked questions about stainless steel hoses – threads, lengths, pressure, replacement

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Common questions about stainless steel hoses – threads, lengths, pressure, replacement

Stainless steel hoses are among the most frequently replaced components in the bathroom and kitchen. At first glance, it seems to be a trivial part – a piece of braiding with two ends – but when it comes to selection and installation, we encounter surprisingly many questions. What is the correct thread? What length to choose? Will the hose withstand the pressure of municipal water? When is it time to replace it? In this article, we have gathered real questions that customers ask most often and answer them as you would hear from an experienced plumber, not from the marketing department.

If you are looking for an introductory overview of what all influences the selection of a hose, we recommend starting with the article How to choose the right stainless steel hose for drinking water in our Knowledge Center. Here we focus specifically on common dilemmas and technical details that are often a source of frustration during selection.

Threads: what do 3/8" and 1/2" mean and how to recognize them?

This is undoubtedly the most common question. The letters and numbers on the hose may sound foreign, but the logic behind them is simple. These are inch threads according to the BSP (British Standard Pipe) standard, where the number refers to the nominal pipe size in inches – not the outer diameter of the thread itself.

3/8" (read: three-eighths of an inch) has an outer thread diameter of approximately 16.7 mm. You will typically encounter it on basin tap connections, corner valves under the sink, or on supply hoses for toilet cisterns. It is a smaller, more slender thread.

1/2" (half an inch) has an outer diameter of about 20.9 mm. It is significantly more robust and can be easily distinguished by the naked eye. This thread is found on most shower taps, kitchen taps, as well as on corner valves for larger toilet ceramics and on many water supplies for washing machines or dishwashers.

Practical tip from the field: if you are unsure, unscrew the old hose and take it with you to the store, or simply measure the outer diameter of the thread on the corner valve with a sliding caliper (a tape measure). If you get a value around 17 mm, it is 3/8". If it is around 21 mm, it is 1/2". Trying to force an incorrect thread is a sure way to damage the thread or cause a water leak.

The marking FF (Female-Female, i.e., female-female) means that both ends of the hose have internal threads and are mounted on the external thread of the corner valve and the tap outlet. This is by far the most common configuration for connecting taps under the sink or in the kitchen. A more detailed discussion of this topic is available in our article Thread 3/8" or 1/2" – how to find out what you need.

Hose length: fixed, extendable, and how many centimeters do you need?

The second most common question. A classic fixed-length hose has a given length and you can't do anything about it. If the space under the sink is tight, or if the corner valve is a bit further from the tap than expected, a fixed-length hose is either too short or bent into an uncomfortable arc that puts stress on the threads.

Extendable hoses elegantly solve this problem: an internal wire in the spiral braiding extends and the hose finds a comfortable route without tension. It is important to know that an extendable hose always has a specified length range – for example, 30–60 cm or 40–80 cm. The minimum length is the compressed state, the maximum is fully extended. In practice, it works best somewhere in the middle of this range – pulling it all the way to the maximum is not ideal, as it increases the stress on the hose.

How to correctly measure the required length? The procedure is simple:

Unscrew the old hose (or install it and throw a string/ruler).
Measure the distance from the center point of the corner valve thread to the center point of the tap outlet thread.
Add 5–8 cm for an arc – the hose should not go straight like a rope, but in a gentle arc so that it does not stress the threads in case of movement under the sink.
The result is your ideal length. If it falls between two fixed lengths, go for the extendable version covering that range.

From practice: a very common dimension under the sink is 30–50 cm, for kitchen faucets 40–60 cm, for shower faucets or lower-mounted corner valves (e.g. for a WC set) even 60–100 cm and more. If you need to connect a washing machine or a dishwasher, you usually go for 100–160 cm.

For convenient installation in a standard bathroom, we recommend for example Stainless steel adjustable hose PROFI MW 1/2" FF, 30–60 cm for shorter runs, or version PROFI MW 1/2" FF, 40–80 cm if you have a bit more space to maneuver. For longer runs (e.g. under a high-mounted shower faucet or to a washing machine), there is PROFI MW 1/2" FF, 80–160 cm.

More on this topic can also be found in the article What hose length suits me – fixed or adjustable?

Working pressure and temperature: what can the hose really withstand?

Stainless steel braided hoses for drinking water are typically dimensioned for much higher pressure than actually occurs in a standard apartment water supply. Let's look at some concrete numbers.

In Slovak apartment buildings, the operating pressure typically ranges between 2.5 and 5 bar. In family homes connected to the public water supply, it can be 3–6 bar, and in homes with a private well and a hydro pump, it can sometimes be even less. High-quality stainless steel hoses for drinking water are certified for an operating pressure of 10 bar (some types up to 16 bar) and test pressures reach 15–25 bar. In other words, under normal operating pressure, bursting a properly installed hose due to pressure is not a realistic risk.

Risks, however, come from other causes:

Mechanical damage – kinks, cracks, abrasion from a sharp edge of the cabinet under the sink, prolonged friction.
Corrosion – with low-quality hoses or when in contact with strong chemicals (descaling agents, etc.).
Material fatigue – after years of operation, the rubber sealing in the fitting degrades.
Hydraulic shocks – when closing water taps quickly, pressure spikes (so-called water hammer) can occur, which temporarily multiply the operating pressure several times.

As for temperature: hoses for drinking water are typically dimensioned for a maximum water temperature of 90–95 °C at lower pressure, and in practice, they handle the normal temperature range of cold and hot water (up to 70 °C at full pressure) without problems. For hot radiator systems, there are special types of hoses – do not confuse standard rubber-sealed drinking water hoses with heating system circuits.

Brass vs. stainless steel fittings – does it even matter?

Yes, it does – although not catastrophically, it's good to know the differences. Hoses in the PROFI series offer both variants.

Brass fittings are cheaper to manufacture, mechanically durable, and long-lasting when properly installed. Their weakness is that they can oxidize and turn green on the surface in an aggressive environment (soft water, acidic cleaning agents, humidity). For drinking water, it is important that the brass meets the requirements for lead content according to current standards (EN 15664 and DWI guidelines) – high-quality products meet this, while cheap unknown brands may not always.

Stainless steel fittings are more resistant to corrosion, remain shiny and clean for longer visually, and do not raise any doubts about metal leaching when in contact with drinking water. For households with more sensitive requirements for drinking water quality (infants, immunocompromised individuals), this is a better choice. Their drawback is a slightly higher price.

If you are looking for clean stainless steel from the braid to the fittings, take a look at Stainless steel adjustable hose PROFI S with stainless steel fittings (1/2" FF, 50–100 cm). For standard use, brass fittings on PROFI MW hoses are fully sufficient – see for example PROFI MW 3/8" FF, 30–60 cm with brass fittings. A more detailed analysis can be found in the article Stainless steel vs. brass fittings – what is the difference and what to choose.

Hose covered in plastic vs. bare stainless steel – a practical perspective

Another nuance customers deal with: why do some hoses look metallic and others are covered in colored plastic?

Bare stainless steel braid is more aesthetically appealing, the stainless steel is visible and gives a premium look. When touched, it is neither warm nor cold, just metallic. The downside: the braid can mechanically damage adjacent hoses, furniture, or pipe insulation when in contact. It also collects dust and shows limescale from drips.

Plastic coating (usually PVC or polyester) protects the stainless steel braid from mechanical damage, provides some insulation, prevents direct contact between metal and other surfaces, and is easier to clean. It is a practical solution for installation in tight spaces under the sink. It is not a sign of lower quality – the inside (pressure hose and braid) is the same.

Read more on this topic in the article Stainless steel hose covered in plastic vs. bare stainless steel – which is better.

Hose replacement: when is it necessary and when is it just unnecessary panic?

This is a question where customers make mistakes on both sides – some change their hoses unnecessarily often, while others wait until the hose actually bursts and floods the bathroom or kitchen cabinet.

The average lifespan of a quality stainless steel water supply hose is 10–15 years under normal operating conditions. Some hoses may last longer, but the rubber sealing ring in the fittings has its physical lifespan – rubber ages, hardens, and cracks regardless of whether the hose visibly corrodes or not.

When to replace the hose:

Visible damage to the braiding (cracks, torn wires, mechanical cuts).
Dripping or moisture at the threads (this does not necessarily mean replacement is needed – sometimes tightening is enough, but a leaking hose should never be ignored).
The hose is older than 10 years and you do not know what type of sealing ring it has (during bathroom renovation, always replace the hoses as well, they are cheap).
The hose is bent into a sharp fold or has been under mechanical stress for a long time.
After a flood or chemical contamination – hoses that have come into contact with contaminated water should be replaced.
If you have bought an apartment from an old owner and do not know when the hoses were installed – do not rely only on those that look clearly old, but replace all of them as a precaution.

When replacement is not necessary:

The hose has a greenish patina on the brass fitting, but shows no moisture – this is natural oxidation, not a safety issue.
The hose is 5 years old, not damaged, and only the color of the plastic cover has changed – this does not affect functionality.

Practical tip: when renovating a bathroom and replacing the faucet, always prepare new hoses of the same dimensions – they are a crown expense compared to an extra hour of plumber's work if you had to order the hose separately.

Article How long does a stainless steel hose last and when to replace it in our Knowledge Center discusses this topic in even more detail.

Installation: what to watch out for to prevent the hose from leaking?

Stainless steel water supply hoses have a built-in rubber sealing ring (flat or conical) in the fittings. This sealing ring performs the entire sealing function – unlike threads, where sealing tape or hemp is sometimes used, the sealing ring in the hose does not require any additional sealing. On the contrary – Teflon or hemp on hoses with flat sealing can make things worse.

The correct installation procedure is as follows:

Check whether the sealing ring in the fitting is present and not cracked (it is always the case with new hoses, but with used or old hoses, verify it).
Clean the threads of the angle valve and the faucet outlet from old sealing material, limescale, and dirt.
Thread the hose by hand – it should not slide or go under the bend. If it is difficult from the start, check whether it is not an incorrect thread or something is catching.
Tighten with a wrench (French or appropriate pipe wrench) only enough to make the joint tight – usually 1–2 turns after tightening by hand is sufficient. Over-tightening the thread is worse than an under-tightened joint, as it can damage the thread or crack the sealing ring.
After turning on the water, check both joints, wait at least 30 minutes, and check again.

A detailed procedure including solutions for problematic situations (old threads, limited space, combining different sizes) can be found in the article Installation of a stainless steel hose under the sink or to the faucet.

Certificates and drinking water: what is important to know?

Hoses that come into contact with drinking water must meet health requirements. In practice, this means that all materials in contact with water – the internal pressure hose, sealing rings, and metal fittings – must not release harmful substances into the water.

Key certificates and standards to ask for or look for in technical documentation when purchasing:

EN 15664 – European standard for metallic materials in contact with drinking water, including brass.
KTW / W270 (Germany) – German hygiene certificates for plastic and elastomeric materials in contact with drinking water. Stricter than many other standards.
WRAS (United Kingdom) – certification for the British market, recognized in other countries as a quality assurance.
ACS (France) – French hygiene certificate.

Products from the PROFI series on atria.sk meet the requirements for drinking water. More on this topic can be read in the article Stainless steel hoses and drinking water – certificates, non-harmfulness, what to watch for.

Why does the hose leak immediately after installation?

If the hose leaks at the joint right after installation, the causes are usually the following (listed from the most common):

The sealing ring is shifted or missing – check visually before installation.
The thread is not tightened enough – tighten with a wrench, remember that tightening by hand is usually not enough.
The thread is over-tightened or damaged – inspect the thread of the angle valve, if damaged, the valve needs to be replaced.
Incorrect thread – a 3/8" hose on a 1/2" angle valve will always leak, because the threads do not match.
The sealing ring is old or cracked – when replacing the sealing ring, it is usually enough to buy a new ball or flat sealing ring of the correct diameter.

A detailed procedure for diagnosis and repair can be found in the article Why the hose leaks or drips at the joints – causes and repair.

Most frequently asked questions (FAQ)

Can I use a 3/8" hose on a 1/2" angle valve?

No, the threads are different sizes and not interchangeable. You won't be able to properly connect a 3/8" hose to a 1/2" valve – the thread will either not engage at all or only partially, which leads to water leakage. The solution is to either buy a hose with the correct thread or use a reducer 3/8" → 1/2" (available in plumbing fittings). If you're unsure about the size of your angle valve, read the article 3/8" or 1/2" thread – how to determine what you need.

Do I need to use Teflon tape when installing a stainless steel hose?

No, and it can actually be harmful. Hoses with flat gaskets (which is standard for stainless steel hoses for drinking water) seal with a flat gasket, not with a threaded seal. If you add Teflon tape to this connection, it can prevent the gasket from seating properly on the flat surface and the connection may paradoxically leak. Use Teflon only where there is no gasket and the seal is formed by the thread itself (e.g., conical metal threads).

How much pressure can a standard apartment hose withstand?

Standard stainless steel hoses for drinking water are designed for a minimum working pressure of 10 bar, with test pressures usually between 15–25 bar. The typical pressure in an apartment's water supply is 3–5 bar, so you have a significant safety margin. A hose under normal pressure will not burst when installed correctly. The risk of water leakage under normal operating pressure comes exclusively from poor sealing at the threads, mechanical damage to the braiding, or degradation of the gasket over time.

How long will a stainless steel hose last?

With a quality hose, proper installation, and normal operating conditions (drinking water, temperature up to 70 °C, pressure up to 6 bar), you can expect a lifespan of 10–15 years. The limiting factor is usually the rubber gasket in the fittings, which hardens and cracks over time. Therefore, we recommend replacing hoses during renovations if they are older than 10 years, even if they look fine. A single drop of water from a cracked hose behind closed kitchen cabinet doors can cause thousands of euros in damage within a week.

Can I extend a retractable hose to its maximum length?

Technically yes, the hose is designed for the full range. However, in practice, it's suboptimal – at maximum extension, the braiding is under higher tension and the hose appears straighter, which puts stress on the threads. We recommend working within 70–85% of the maximum length, so the hose has a slight natural curve. This curve compensates for any vibrations or movements of the valve.

Can I use a stainless steel hose for hot heating (radiator)?

It is not recommended. Hoses for drinking water are indeed rated for temperatures up to around 90–95 °C, but the rubber gaskets in them are not designed for continuous contact with hot heating water, which has a different chemical composition than drinking water (corrosion inhibitors, lower oxygen content, possible other additives). There are special types of hoses for heating systems – with more durable gaskets and a different inner layer. It is not recommended to interchange these two types.

Summary: what not to forget when choosing and replacing a stainless steel hose

A stainless steel hose is a simple product, but choosing the right one requires attention to several key parameters. We summarize them in a simple checklist:

Thread: Determine the thread size on the angle valve and the battery outlet – most commonly 3/8" or 1/2", both as FF (internal thread on both ends of the hose).
Length: Measure the actual distance and add a margin for the curve. If you're unsure, choose an extendable hose with an appropriate range.
Type of fittings: Brass fittings are sufficient for standard use, while stainless steel fittings are recommended for higher hygiene requirements for drinking water.
Coating: A plastic cover is more practical for tight spaces, while bare stainless steel is more aesthetic – both are functionally equivalent.
Pressure and temperature: Standard hoses easily handle normal apartment conditions with a large margin of safety.
Installation without Teflon: The gasket in the fitting does all the work, do not add Teflon.
Preventive replacement: Replace hoses preventively after 10 years, even if they look fine.

If you're looking for a specific product, the category Stainless Steel Hoses covers both standard and more specialized situations – from compact extendable hoses for sinks to long hoses for showers or washing machines. Recommended products have been mentioned throughout this article, according to specific situations and requirements.

Do you have a question about this topic?

Not sure how to decide or dealing with a specific situation in your home? Write to us – we're happy to help.